Printhead structure

ABSTRACT

This invention relates to an ink supply arrangement for a printhead of an print engine. The printhead has an array of MEMS ink ejection devices mounted on a surface of a wafer and an ink supply passage extending through the wafer from an opposed surface of the wafer to each ink ejection device. The ink ejection devices are arranged in groups. Accordingly, the ink supply arrangement includes a block of silicon material mountable on the opposed surface of the wafer. The block has a plurality of channels defined therein which open out into a first surface of the block in abutment with the opposed surface of the wafer. Ink supply inlet openings are in communication with each channel. These inlet openings open out into a second surface of the block.

[0001] Continuation application of U.S. Ser. No. 09/608,779 filed onJun. 30, 2000

FIELD OF THE INVENTION

[0002] This invention relates to a print engine. The invention hasparticular application in a print engine for use in an instantaneousprint, digital camera. More particularly, the invention relates to anink supply assembly for supplying ink to a printhead of the printengine.

BACKGROUND TO THE INVENTION

[0003] It will be appreciated that a printhead of the printer engine ofa page width printer has a width dimension measured in fractions ofmillimeters. Typically the printhead has a width dimension of about sixhundred micrometers. In an array of ink jet nozzles, adjacent nozzlescould be spaced from each other by dimensions in the order of 100micrometers. While the substrate of the printhead is made from a siliconwafer a supply mechanism for supplying ink to the substrate is oftenmade out of plastic. To mold the plastic such that individual inksupplies are provided to each ink supply passage in the substrateresults in extremely fine tolerances with the consequential expense,which that entails.

[0004] By quote “page width” is meant that the printhead prints one lineat a time on the print media without traversing the print media, orrastering, as the print media moves past the printhead.

SUMMARY OF THE INVENTION

[0005] According to one aspect of the invention there is provided aprint engine comprising:

[0006] a plurality of ink reservoirs;

[0007] a plurality of first passages each in fluid flow communicationwith a respective reservoir;

[0008] a plurality of second passages, each corresponding to arespective first passage, the second passages being spaced from thefirst passages;

[0009] a plurality of third passages, each connecting, in fluid flowcommunication, a respective first passage and the corresponding secondpassage; and

[0010] a plurality of microelectromechanical (MEMS) ink ejection devicesconnected in fluid flow communication with each second passage.

[0011] According to a further aspect of the invention there is providedan elongate printhead structure comprising:

[0012] a plurality of first parallel ink passages extendinglongitudinally relative to the printhead;

[0013] a plurality of second parallel ink passages, spaced from thefirst passages and extending longitudinally relative to the printhead,each second passage corresponding to a respective one of said firstpassages;

[0014] a plurality of third passages each opening into a respectivesecond passage, and connecting that passage in fluid flow communicationwith the corresponding first passage, wherein each third passage extendssubstantially transversely relative to the printhead;

[0015] a plurality of fourth passages opening into each second passage,each fourth passage extending substantially transversely relative to theprinthead; and

[0016] a plurality of individual microelectromechanical (MEMS) inkejection devices, each device being connected with a respective fourthpassage.

[0017] Preferably, each second passage is of smaller width than therespective corresponding first passage.

[0018] Preferably, the structure further comprises an ink distributormoulding defining a plurality of channels, each channel correspondingwith, and opening into, a respective first passage. Each channel ispreferably connected with an end of the respective first passage and ispreferably connected in fluid flow communication with an ink supplyreservoir.

[0019] The structure preferably further comprises a first silicon waferwhich defines at least part of each second passage and each thirdpassage. The structure also preferably further comprises a secondsilicon wafer which is superposed on the first wafer and which definessaid fourth passages. Preferably, the second silicon wafer defines partof each second passage. Each second passage preferably extends along,and opens through, a face of the first wafer, the second wafer beingjoined to said face.

[0020] Preferably, the structure further comprises a pair of elongateprinthead components, one of said components defining a plurality oflongitudinal recesses and the other of said components covering saidrecesses so that the recesses constitute said first passages. Said onecomponent preferably defines at least a part of each third passage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The invention will now be described by way of example withreference to the accompanying diagrammatic drawings in which:—

[0022]FIG. 1 shows a three dimensional view of a print engine, includingcomponents in accordance with the invention;

[0023]FIG. 2 shows a three dimensional, exploded view of the printengine;

[0024]FIG. 3 shows a three dimensional view of the print engine with aremovable print cartridge used with the print engine removed;

[0025]FIG. 4 shows a three dimensional, rear view of the print enginewith the print cartridge shown in dotted lines;

[0026]FIG. 5 shows a three dimensional, sectional view of the printengine;

[0027]FIG. 6 shows a three dimensional, exploded view of a printheadsub-assembly of the print engine;

[0028]FIG. 7 shows a partly cutaway view of the printhead sub-assembly;

[0029]FIG. 8 shows a sectional end view of the printhead sub-assemblywith a capping mechanism in a capping position;

[0030]FIG. 9 shows the printhead sub-assembly with the capping mechanismin its uncapped position;

[0031]FIG. 10 shows a schematic, three dimensional view of part of anink supply arrangement, in accordance with the invention, for aprinthead of a print engine;

[0032]FIG. 11 shows a schematic, sectional end view of the ink supplyarrangement taking along line XI-XI in FIG. 10;

[0033]FIG. 12 shows a schematic, sectional end view of the ink supplyarrangement taken along line XII-XII in FIG. 10;

[0034]FIG. 13 shows a schematic, sectional end view of the ink supplyarrangement taken along line XIII-XIII in FIG. 10; and

[0035]FIG. 14 shows a schematic, sectional end view of the ink supplyarrangement taken along line XIV-XIV in FIG. 10.

DETAILED DESCRIPTION OF THE DRAWINGS

[0036] In the drawings, reference numeral 500 generally designates aprint engine, in accordance with the invention. The print engine 500includes a print engine assembly 502 on which a print roll cartridge 504is removably mountable.

[0037] The print cartridge 504 is described in greater detail in ourco-pending applications entitled “A Print Cartridge” (docket numberCA02US) and “An Ink Cartridge” (docket number CA04US) filedsimultaneously herewith as U.S. Ser. Nos. 09/607,993 and 09/607,251respectively, the contents of that disclosure being specificallyincorporated herein by reference.

[0038] The print engine assembly 502 comprises a first sub-assembly 506and a second, printhead sub-assembly 508.

[0039] The sub-assembly 506 includes a chassis 510. The chassis 510comprises a first molding 512 in which ink supply channels 514 aremolded. The ink supply channels 514 supply inks from the print cartridge504 to a printhead 516 (FIGS. 5 to 7) of the printhead sub-assembly 508.The printhead 516 prints in four colors or three colors plus ink whichis visible in the infrared light spectrum only (hereinafter referred toas ‘infrared ink’). Accordingly, four ink supply channels 514 aredefined in the molding 512 together with an air supply channel 518. Theair supply channel 518 supplies air to the printhead 516 to inhibit thebuild up of foreign particles on a nozzle guard of the printhead 516.

[0040] The chassis 510 further includes a cover molding 520. The covermolding 520 supports a pump 522 thereon. The pump 522 is a suction pump,which draws air through an air filter in the print cartridge 504 via anair inlet pin 524 and an air inlet opening 526. Air is expelled throughan outlet opening 528 into the air supply channel 518 of the chassis510.

[0041] The chassis 510 further supports a first drive motor in the formof a stepper motor 530. The stepper motor 530 drives the pump 522 via afirst gear train 532. The stepper motor 530 is also connected to a driveroller 534 (FIG. 5) of a roller assembly 536 of the print cartridge 504via a second gear train 538. The gear train 538 engages an engagableelement 540 (FIG. 2) carried at an end of the drive roller 534. Thestepper motor 530 thus controls the feed of print media 542 to theprinthead 516 of the sub-assembly 508 to enable an image to be printedon the print media 542 as it passes beneath the printhead 516. It alsoto be noted that, as the stepper motor 530 is only operated to advancethe print media 542, the pump 522 is only operational to blow air overthe printhead 516 when printing takes place on the print media 542.

[0042] The molding 512 of the chassis 510 also supports a plurality ofink supply conduits in the form of pins 544 which are in communicationwith the ink supply channels 514. The ink supply pins 544 are receivedthrough an elastomeric collar assembly 546 of the print cartridge 504for drawing ink from ink chambers or reservoirs 548 (FIG. 5) in theprint cartridge 504 to be supplied to the printhead 516.

[0043] A second motor 550, which is a DC motor, is supported on thecover molding 520 of the chassis 510 via clips 552. The motor 550 isprovided to drive a separating means in the form of a cutter armassembly 554 to part a piece of the print media 542, after an image hasbeen printed thereon, from a remainder of the print media. The motor 550carries a beveled gear 556 on an output shaft thereof. The beveled gear556 meshes with a beveled gear 558 carried on a worm gear 560 of thecutter assembly 554. The worm gear 560 is rotatably supported viabearings 562 in a chassis base plate 564 of the printhead sub-assembly508.

[0044] The cutter assembly 554 includes a cutter wheel 566, which issupported on a resiliently flexible arm 568 on a mounting block 570. Theworm gear 560 passes through the mounting block 570 such that, when theworm gear 560 is rotated, the mounting block 570 and the cutter wheel566 traverse the chassis base plate 564. The mounting block 570 bearsagainst a lip 572 of the base plate 564 to inhibit rotation of themounting block 570 relative to the worm gear 560. Further, to effectcutting of the print media 542, the cutter wheel 566 bears against anupper housing or cap portion 574 of the printhead sub-assembly 508. Thiscap portion 574 is a metal portion. Hence, as the cutter wheel 566traverses the capped portion 574, a scissors-like cutting action isimparted to the print media to separate that part of the print media 542on which the image has been printed.

[0045] The sub-assembly 506 includes an ejector mechanism 576. Theejector mechanism 576 is carried on the chassis 510 and has a collar 578having clips 580, which clip and affix the ejector mechanism 576 to thechassis 510. The collar 578 supports an insert 582 of an elastomericmaterial therein. The elastomeric insert 582 defines a plurality ofopenings 584. The openings 584 close off inlet openings of the pins 544to inhibit the ingress of foreign particles into the pins 544 and, in sodoing, into the channels 514 and the printhead 516. In addition, theinsert 584 defines a land or platform 586 which closes off an inletopening of the air inlet pin 524 for the same purposes.

[0046] A coil spring 588 is arranged between the chassis 510 and thecollar 578 to urge the collar 578 to a spaced position relative to thechassis 510 when the cartridge 504 is removed from the print engine 500,as shown in greater detail in FIG. 3 of the drawings. The ejectormechanism 576 is shown in its retracted position in FIG. 4 of thedrawings.

[0047] The printhead sub-assembly 508 includes, as described above, thebase plate 564. A capping mechanism 590 is supported displaceably on thebase plate 564 to be displaceable towards and away from the printhead516. The capping mechanism 590 includes an elongate rib 592 arranged ona carrier 593. The carrier is supported by a displacement mechanism 594,which displaces the rib 592 into abutment with the printhead 516 whenthe printhead 516 is inoperative. Conversely, when the printhead 516 isoperational, the displacement mechanism 594 is operable to retract therib 592 out of abutment with the printhead 516.

[0048] The printhead sub-assembly 508 includes a printhead supportmolding 596 on which the printhead 516 is mounted. The molding 596,together with an insert 599 arranged in the molding 596, define apassage 598 through which the print media 542 passes when an image is tobe printed thereon. A groove 700 is defined in the molding 596 throughwhich the capping mechanism 590 projects when the capping mechanism 590is in its capping position.

[0049] An ink feed arrangement 702 is supported by the insert 599beneath the cap portion 574. The ink feed arrangement 702 comprises aspine portion 704 and a casing 706 mounted on the spine portion 704. Thespine portion 704 and the casing 706, between them, define ink feedgalleries 708 which are in communication with the ink supply channels514 in the chassis 510 for feeding ink via passages 710 (FIG. 7) to theprinthead 516.

[0050] An air supply channel 711 (FIG. 8) is defined in the spineportion 704, alongside the printhead 516.

[0051] Electrical signals are provided to the printhead 516 via a TABfilm 712 which is held captive between the insert 599 and the ink feedarrangement 702.

[0052] The molding 596 includes an angled wing portion 714. A flexibleprinted circuit board (PCB) 716 is supported on and secured to the wingportion 714. The flex PCB 716 makes electrical contact with the TAB film712 by being urged into engagement with the TAB film 712 via a rib 718of the insert 599. The flex PCB 716 supports busbars 720 thereon. Thebusbars 720 provide power to the printhead 516 and to the other poweredcomponents of the print engine 500. Further, a camera print enginecontrol chip 721 is supported on the flex PCB 716 together with a QAchip (not shown) which authenticates that the cartridge 504 iscompatible and compliant with the print engine 500. For this purpose,the PCB 716 includes contacts 723 which engage contacts 725 in the printcartridge 504.

[0053] As illustrated more clearly in FIG. 7 of the drawings, theprinthead itself includes a nozzle guard 722 arranged on a silicon wafer724. The ink is supplied to a nozzle array (not shown) of the printhead516 via an ink supply member 726. The ink supply member 726 communicateswith outlets of the passages 710 of the ink feed arrangement 702 forfeeding ink to the array of nozzles of the printhead 516, on demand.

[0054] The arrangement of the printhead is shown in greater detail inFIGS. 10 to 14 of the drawings. The ink supply member 726 is a block ofsilicon wafer which is mounted on the silicon wafer 724. The member 726has channels 728 formed therein. The channels 728 extend the length ofthe member 726.

[0055] As described above, the printhead 516 is a multi-color printheadhaving nozzles 757 arranged in groups. Each group prints one color orthe infrared ink. The nozzles 757 are MEMS devices mounted on a surface730 of the silicon wafer 724 with the member 726 being mounted on anopposed surface 732 of the silicon wafer 724. Hence, as shown moreclearly in FIG. 10 of the drawings, each group of nozzles 757 issupplied by an ink supply passage 734.

[0056] Thus, each channel 728 of the member 726 communicates with itsassociated group of passages 734. Each channel 728 has a plurality ofink inlet openings 736, 738, 740 and 742. For example, the ink inletopenings 736 supply black ink to the first group of ink supply passages734 of the wafer 724. Instead, where three colors and infrared ink areprovided, the ink inlet openings 736 provide infrared ink to the firstgroup of passages. The inlet openings 738 provide magenta ink to thesecond group of nozzles via their inlet passages 734. The ink inletopenings 740 provide yellow ink to the third group of nozzles via theirpassages 734. The final group of inlet openings 742 provide cyan ink tothe fourth group of nozzles via their passages 734.

[0057] Each inlet opening 736, 738, 740, 742 is isolated from itsneighboring opening via a transversely extending bead of sealingmaterial 744. It will be appreciated that the ink feed arrangement 702bears against the top surface 746 of the member 726 further to isolatethe openings 736 to 742 from one another.

[0058] Also, it is to be noted that the TAB film 712 is bonded to thesurface 730 of the wafer 724 via beads of adhesive 748. The beads 748further form a fluid tight seal against the side of the wafer 724.

[0059] Ink ejected from each MEMS device 757 is ejected through apassage 750 in the nozzle guard 722. To maintain a surface 752 of thenozzle guard and a region 754 between the nozzle guard 722 and the wafer724 free of foreign particles, air is blown on to the surface 752 of thenozzle guard 722 and, via inlet openings 756 from the channel 710 intothe region 754.

[0060] The member 726 is a silicon wafer and, accordingly, the channels728 and the inlet openings 736 to 742 are formed in the wafer by etchingtechniques.

[0061] As described in the introduction to the specification, thespacing between the passages 734 and the wafer 724 is of the order ofone hundred micrometers. In contrast, each ink inlet opening 736 to 742has a length dimension L of approximately 0.5 millimeters. The spacingbetween adjacent inlet openings is also of the order of 0.5 millimeters.If one considers the width dimension of the printhead 516 as the Xdimension with a length of the printhead as a Y dimension the ink supplymember 726 effectively functions as an adapter converting a small Xdimension into a much larger Y dimension. Accordingly, it is easier tofabricate the feed passages of the ink feed arrangement 702, which is aplastic molding, than would be the case if the ink feed arrangement fedthe ink directly into the wafer 724 of the printhead 516.

[0062] It will be appreciated by persons skilled in the art thatnumerous variations and/or modifications may be made to the invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects as illustrative and notrestrictive.

We claim:
 1. A print engine comprising: a plurality of ink reservoirs; aplurality of first passages each in fluid flow communication with arespective reservoir; a plurality of second passages, each correspondingto a respective first passage, the second passages being spaced from thefirst passages; a plurality of third passages, each connecting, in fluidflow communication, a respective first passage and the correspondingsecond passage; and a plurality of microelectromechanical (MEMS) inkejection devices connected in fluid flow communication with each secondpassage.
 2. An elongate printhead structure comprising: a plurality offirst parallel ink passages extending longitudinally relative to theprinthead; a plurality of second parallel ink passages, spaced from thefirst passages and extending longitudinally relative to the printhead,each second passage corresponding to a respective one of said firstpassages; a plurality of third passages each opening into a respectivesecond passage, and connecting that passage in fluid flow communicationwith the corresponding first passage, wherein each third passage extendssubstantially transversely relative to the printhead; a plurality offourth passages opening into each second passage, each fourth passageextending substantially transversely relative to the printhead; and aplurality of individual microelectromechanical (MEMS) ink ejectiondevices, each device being connected with a respective fourth passage.3. The structure of claim 2 wherein each second passage is of smallerwidth than the respective corresponding first passage.
 4. The structureof claim 2 further comprising an ink distributor moulding defining aplurality of channels, each channel corresponding with, and openinginto, a respective first passage.
 5. The structure of claim 4 whereineach channel is connected with an end of the respective first passage.6. The structure of claim 4 wherein each channel is connected in fluidflow communication with an ink supply reservoir.
 7. The structure ofclaim 2 further comprising a first silicon wafer which defines at leastpart of each second passage and each third passage.
 8. The structure ofclaim 7 further comprising a second silicon wafer which is superposed onthe first wafer and which defines said fourth passages.
 9. The structureof claim 8 wherein the second silicon wafer defines part of each secondpassage.
 10. The structure of claim 8 wherein each second passageextends along, and opens through, a face of the first wafer, the secondwafer being joined to said face.
 11. The structure of claim 2 furthercomprising a pair of elongate printhead components, one of saidcomponents defining a plurality of longitudinal recesses and the otherof said components covering said recesses so that the recessesconstitute said first passages.
 12. The structure of claim 11 whereinsaid one component defines at least a part of each third passage.